For certain kinds of classification systems, for the mounting of paper sheets in collections or for reinforcement purposes, it has been common heretofore to apply to sheets, along at least one of the edges thereof, a set of perforation which can, for example, be adapted to the type of classification system which is used. A typical classification system cf this type, of course, utilizes rods or needles which can be threaded through intact perforations to support the sheets while perforations which have been opened allow other sheets to drop from a sheet.
A particularly convenient method of applying these perforations to a sheet and in general for applying perforations to a sheet, involves the application of a perforated, semirigid band, strip or tape of a synthetic resin or plastic along a nonperforated edge of the sheet.
This band thus also constitutes a reinforcing band for the edge of the sheet. The reinforcing band is formed longitudinally over a first half of the width of the tape with the perforations and over a second half of the tape is covered by a longitudinal layer of a contact o r pressure adhesive so that the tape is a self-adhesive tape.
Customarily, the self-adhesive layer is itself covered for storage and handling by a thin protective band or strip, also of a synthetic resin or plastic material, which is more flexible than the perforated tape and which can be drawn off from the perforated tape before use of the latter. This strippable band can be referred to conveniently as a masking band or strip because it prevents premature contact of the adhesive layer with a substrate, with the fingers or with any applicator which may be used.
The reinforcing or classifying strips thus described have generally been provided heretofore as rectangular strips precut to standard lengths corresponding to the lengths of the frontal edges of the sheets to which they are to be applied. They also may be provided in continuous rolls respectively received in a receptacle or dispenser from which the tape can be fed.
Utilization of such classifier strips requires cutting the strip to length, removing the masking strip covering the self-adhesive half of the tape, placing the classifying tape along the edge of the sheet so that the self-adhesive half covers the sheet, and application of high pressure against the tape to bond the latter to the underlying sheet.
These operations require utmost care and attention since the danger of misalignment or slipping is great. Indeed such classifying tapes cannot be applied without a high degree of waste except by highly skilled and proficient individuals.